JP6486095B2 - Nonwoven manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a nonwoven fabric using a heat-extensible fiber as a raw material.

  As conventional techniques related to nonwoven fabrics using heat-extensible fibers as raw materials, for example, those described in Patent Documents 1 and 2 are known. In Patent Document 1, hot air is blown to a web containing a heat-extensible fiber by an air-through method, and an intersection between the constituent fibers of the web is fused to form a bonded web in which the constituent fibers are bonded to each other. Describes a method for producing a nonwoven fabric having an uneven surface by embossing a bonded web with an embossing device provided with an embossing roll having unevenness and a flat roll having a smooth peripheral surface. In this document, the temperature of the hot air blown onto the web is set to be equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component. In the embossing process, the hot air blowing surface of the bonded web is brought into contact with the embossing roll, and the surface opposite to the hot air blowing surface is brought into contact with the flat roll.

  Patent Document 2 describes a non-woven fabric that includes a heat-extensible fiber that is elongated by heating and has a large number of convex portions and concave portions on one surface side. As for the fiber which comprises a convex part, the thermal expansion rate is higher in the upper part than the lower part of the convex part. In this nonwoven fabric, the upper part side of a convex part is formed using a heat | fever extensible raw material fiber, and the lower part side of a convex part is formed using the non-heat extensible raw material fiber. And when this nonwoven fabric is used as a surface sheet of an absorbent article, it is described in this document that the liquid permeability of the surface sheet is increased and the liquid that has passed through is less likely to reverse.

JP 2011-137249 A JP 2011-252252 A

  According to the techniques described in Patent Documents 1 and 2, a bulky nonwoven fabric is obtained. However, it is not easy to further increase the bulkiness of the nonwoven fabric using the techniques described in these documents, and to improve the absorption performance when the nonwoven fabric is used for absorbent articles.

  Therefore, the subject of this invention exists in improvement of the manufacturing method of a nonwoven fabric, and provides the manufacturing method which can improve the characteristic of the nonwoven fabric which used the heat | fever extensible fiber as a raw material in more detail.

The present invention provides a web production process for producing a web containing a heat-fusible core-sheath composite fiber having a shrinkage rate at 80 ° C. of 0% or more and an elongation rate at 136 ° C. of 8% or more,
Embossing the web manufactured in the web manufacturing process, and embossing process to obtain an embossed web by fixing the constituent fibers of the web at a plurality of embossed portions formed thereby, and air through the embossed web A method of manufacturing a nonwoven fabric having an air-through process of blowing hot air in a method,
Prior to embossing, the heat-fusible core-sheath composite fiber is heat-treated at a temperature not less than the glass transition point of the resin constituting the core and lower than the thermal elongation start temperature, and the heat-fusible core-sheath Once the mold composite fiber is shrunk,
A method for producing a nonwoven fabric, wherein the blowing of the hot air in an air-through method is performed at a temperature equal to or higher than the thermal expansion start temperature of the heat-fusible core-sheath composite fiber, and the heat-fusible core-sheath composite fiber is stretched. It is to provide.

  According to the production method of the present invention, it is possible to easily produce a non-woven fabric that is bulky and can reduce the liquid spread when used as a top sheet of an absorbent article.

It is a graph which shows the relationship between the temperature and fiber length of the heat-fusible core-sheath-type composite fiber used with the manufacturing method of this invention.

Hereinafter, the present invention will be described based on preferred embodiments thereof. The manufacturing method of the nonwoven fabric of this invention has one of the characteristics in using the heat | fever extensible fiber which has a specific property as raw material fiber. And in the manufacturing method of this invention, the following processes (a) thru | or (c) are performed using such a specific heat | fever extensible fiber.
(A) Web manufacturing process (b) Web embossing process (c) Air-through process

  The heat-extensible fiber used in the present invention is composed of a heat-fusible core-sheath composite fiber having a shrinkage rate at 80 ° C. of 0% or more and an extension rate at 136 ° C. of 6% or more. Hereinafter, for the sake of simplicity, this fiber is referred to as “heat-extensible composite fiber”. When the heat-extensible composite fiber is heated from room temperature, its length decreases, that is, shrinks at a temperature of 80 ° C. or lower. When the heating is further performed and the temperature is further increased, the contraction stops and the contraction is changed to the extension. At least at 136 ° C., the length is longer than that before heating. This change is represented in a graph as shown in FIG. 1, for example. In FIG. 1, the horizontal axis represents the heating temperature of the heat-extensible composite fiber. The heating rate is constant. The vertical axis indicates the rate of expansion or contraction from the length before heating. As shown in the figure, it is understood that when heating is started, the shrinkage rate of the heat-extensible conjugate fiber increases and the length becomes shorter. And the shrinkage rate becomes maximum at around 80 ° C. That is, the fiber length is the shortest. As the temperature rises further than this maximum value, the shrinkage rate decreases. That is, the length becomes longer as compared with the maximum contraction rate state. In other words, it turns from contraction to extension. And at 90 degreeC vicinity, the expansion | extension rate of a heat | fever extensible composite fiber will be zero, and will return to the length of the state before a heating. When the temperature further increases, the heat-extensible composite fiber is stretched more than the length before heating. The heat-extensible composite fiber includes a core component and a sheath component. In the following description, the core component is also referred to as a fiber-forming resin component, a high melting point component, or a first resin component. The sheath component is also referred to as a heat-adhesive resin component, a low melting point component, or a second resin component.

The thermal contraction rate of the heat-extensible composite fiber is measured by the following method. A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used. A sample is prepared by collecting a plurality of fibers having a fiber length of 10 mm or more so that the total mass per fiber length of 10 mm is 0.5 mg. After arranging the plurality of fibers in parallel, the fibers are mounted on the apparatus at a chuck distance of 10 mm. The measurement start temperature is 25 ° C., and the temperature is increased at a temperature increase rate of 5 ° C./min with a constant load of 0.73 mN / dtex applied. The amount of elongation of the fiber at that time is measured, and the amount of elongation at that temperature is read. When the amount of elongation is BX mm, the thermal elongation rate is expressed by the following equation.
(BX / 10) x 100 (%)
The absolute value of the value when the thermal expansion rate is less than 0 is defined as the thermal contraction rate of the temperature at that time.

On the other hand, the thermal elongation rate of the thermally extensible composite fiber is measured by the following method. It is measured by the same method as the thermal shrinkage rate, and the thermal elongation rate is expressed by the following equation.
(BX / 10) x 100 (%)
The absolute value of the value when this value is 0 or more is taken as the thermal expansion rate of the temperature at that time.

  The heat-extensible composite fiber exhibiting the heat shrinkage / heat extension behavior as shown in FIG. 1 is based on a known method, for example, according to Example 1 of Japanese Patent Application Laid-Open No. 2007-303035. The drying performed before can be manufactured by processing at normal temperature. In this method, it is preferable to use, for example, polyethylene terephthalate (PET) or polypropylene as the fiber-forming resin component. On the other hand, it is preferable to use a crystalline thermoplastic resin having a melting point lower by 20 ° C. or more than the fiber-forming resin component as the heat-adhesive resin component. Preferable examples of the crystalline thermoplastic resin include polyolefin resins and crystalline copolyesters.

  Examples of the polyolefin resin include polyolefins such as polypropylene, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, or crystalline propylene copolymer composed of propylene and another α-olefin. Or an α-olefin such as ethylene, propylene, butene-1, or pentene-1 and an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, or hymic acid Examples thereof include modified polyolefins composed of a copolymer with at least one comonomer such as an acid, an ester thereof, or an unsaturated compound having a polar group such as an acid anhydride.

  Examples of the above-mentioned crystalline copolyester include, as an acid component, a main dicarboxylic acid component is terephthalic acid or an ester-forming derivative thereof, and a main diol component is ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene. Alkylene terephthalate obtained by combining 1 to 3 kinds of glycols with aromatic dicarboxylic acids such as isophthalic acid, naphthalene-2,6-dicarboxylic acid and 5-sulfoisophthalate, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid Acid, cycloaliphatic dicarboxylic acid such as cyclohexamethylenedicarboxylic acid, ε-hydroxycarboxylic acid, ω-hydroxycarboxylic acid, etc., diol component other than the above examples, polyethylene glycol, polytetramethylene glycol, etc. Examples include those obtained by copolymerizing an aliphatic diol, an alicyclic diol such as cyclohexamethylene dimethanol and the like so as to exhibit a target melting point. The copolymerization rate is desirably variously adjusted by the copolymerization component so as to exhibit the target melting point, but is preferably 5 to 50 mol%.

  The heat-extensible composite fiber used in the present invention has a breaking elongation (JIS L-1015: 2005 8.7.1 method) of 130% or more, in addition to exhibiting the above-described heat shrinkage / heat elongation behavior, It is preferably 170% or more, preferably 1200% or less, and particularly preferably 900% or less. Specifically, it is preferably 130% or more and 1200% or less, and particularly preferably 170% or more and 900% or less. Moreover, it is preferable that 120 degreeC dry heat shrinkage (JIS L-1015: 2005 8.15b) is smaller than -1%.

  As the heat-extensible conjugate fiber that exhibits the heat shrinkage / heat extension behavior as described above and has the mechanical property values as described above, for example, those described in JP-A-2007-303035 are preferably used. it can.

  The heat-extensible conjugate fiber is composed of a first resin component as a core component and a second resin component as a sheath component having a melting point or softening point lower than the melting point of the first resin component, and the second resin component is a fiber. At least a part of the surface is continuously present in the length direction. The 1st resin component in a heat | fever extensible composite fiber is a component which expresses the heat | fever extensibility of this fiber, and a 2nd resin component is a component which expresses heat-fusibility.

  The heat stretchable conjugate fiber can be stretched by heat at a temperature lower than the melting point of the first resin component. The heat-extensible conjugate fiber has a thermal elongation rate of 0.5% or more, particularly 3% at a temperature 10 ° C. higher than the melting point of the second resin component, or 10 ° C. higher than the softening point in the case of a resin having no melting point. In particular, the content is preferably 5% or more, and more preferably 20% or less. Specifically, it is preferably 0.5% or more and 20% or less, more preferably 3% or more and 20% or less, and still more preferably 5% or more and 20% or less.

  The melting points of the first resin component and the second resin component are measured using a differential scanning calorimeter (DSC6200 manufactured by Seiko Instruments Inc.). A finely cut fiber sample (sample weight 2 mg) is subjected to thermal analysis at a heating rate of 10 ° C./min, and the melting peak temperature of each resin is measured. The melting point is defined by its melting peak temperature. When the melting point of the second resin component cannot be clearly measured by this method, this resin is defined as “resin having no melting point”. In this case, the temperature at which the second resin component is fused to such an extent that the fusion point strength of the fiber can be measured is defined as the temperature at which the molecular flow of the second resin component begins.

  In the above-described web production process (a), a web containing the above-described heat-extensible composite fiber is produced. The web may be composed only of the heat-extensible composite fiber, or may include the heat-extensible composite fiber and other fibers. As other fibers, for example, a bicomponent composite fiber that includes a high melting point component and a low melting point component, and the low melting point component continuously exists in the length direction at least part of the fiber surface is used. Can do. This composite fiber is preferably a non-heat-extensible fiber. The composite fiber is preferably a heat-fusible fiber. There are various forms of the composite fiber such as a core-sheath type and a side-by-side type, and any form can be used. When the composite fiber is a heat-fusible fiber, the fiber has been subjected to drawing treatment at the raw material stage. The stretching treatment referred to here is a stretching operation with a stretching ratio of about 2 to 6 times. When the web contains other fibers, the proportion of the other fibers is preferably 10% by mass or more, more preferably 40% by mass or more, and 90% by mass or less with respect to the mass of the web. It is preferable that it is 60 mass% or less. The ratio of the other fibers is preferably 10% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 60% by mass or less with respect to the mass of the web.

  There is no restriction | limiting in particular in the manufacturing method of a web, A conventionally well-known method can be used. For example, when the whole raw fiber including the heat-extensible conjugate fiber is a short fiber, a card method for producing a web using a card machine can be used. In this case, it is preferable that the length of the raw fiber is, for example, 30 mm or more and 70 mm or less in consideration of the passing characteristics of the card machine. When short fibers shorter than this length range are used, an airlaid method can be used as a web manufacturing method. In addition to these web forming methods, a needle punch method or the like can be used.

  Regarding the fineness of the heat-extensible composite fiber, an appropriate value is selected according to the web forming method and the specific use of the target nonwoven fabric. For example, when a web is manufactured by a card machine and the target nonwoven fabric is used as a constituent material of the absorbent article, the fineness of the heat-extensible conjugate fiber is preferably 0.5 dtex or more, and 1.0 dtex or more More preferably, it is preferably 7.0 dtex or less, and more preferably 5.0 dtex or less. The fineness of the heat-extensible conjugate fiber is preferably 0.5 dtex or more and 7.0 dtex or less, and more preferably 1.0 dtex or more and 5.0 dtex or less. The fineness here is the fineness of the heat-extensible conjugate fiber in a state before receiving heat application (that is, a state before shrinkage and elongation are expressed).

The same applies to the basis weight of the web, and an appropriate value is selected according to the specific use of the target nonwoven fabric. For example, when the target nonwoven fabric is used as the constituent material of the absorbent article, the basis weight of the web is preferably 10 g / m ² or more, more preferably 15 g / m ² or more, and 60 g. / M ² or less, more preferably 40 g / m ² or less. The basis weight of the web is preferably 10 g / m ² or more and 60 g / m ² or less, and more preferably 15 g / m ² or more and 40 g / m ² or less.

  The web may have a single layer structure or a multilayer structure. When the web has a single-layer structure, heat-extensible composite fibers are included in the single-layer structure. When the web has a multilayer structure, it is only necessary that at least one layer in the multilayer structure contains a heat-extensible composite fiber. The said one layer may be comprised only from the heat | fever extensible composite fiber, or may be comprised including the heat | fever extensible composite fiber and another fiber. When the web has a multi-layer structure, for example, a number of card machines corresponding to the number of layers are prepared, the webs are stacked using each card machine, and the webs of the target structure are obtained by superimposing the webs. can get.

  When the web is obtained in this way, the embossing step (b) is performed. This step can be performed using, for example, an embossing apparatus provided with a pair of rolls. At least one of the pair of rolls is a sculpture roll in which irregularities are formed on the peripheral surface. The other roll is an anvil roll having a smooth peripheral surface, or a sculpture roll in which concave and convex portions meshing with the one roll are formed on the peripheral surface, or a convex portion of the one roll and a tip-to-two -It is a sculpture roll in which irregularities that contact with the tip are formed on the peripheral surface. Each roll can be made of metal, rubber or paper.

  In the embossing apparatus, when the web passes between a pair of rolls, a plurality of embossed portions are formed on the web by the action of heat and pressure, and the constituent fibers of the web are fixed at the embossed portions. . As a result, the web acquires shape retention and takes the form of a nonwoven fabric. The shape of the embossed portion is appropriately selected according to the specific use of the intended nonwoven fabric, the characteristics required of the nonwoven fabric, and the like. For example, it is possible to form a lattice-like embossed portion formed continuously along the web conveyance direction or an oblique lattice-like embossed portion inclined with respect to the web conveyance direction. Alternatively, the embossed portions can be formed such that small embossed portions such as small dots and rectangles are arranged in various patterns such as a staggered pattern.

  The heat applied to the web in the embossing apparatus is preferably less than the thermal elongation start temperature of the thermally stretchable conjugate fiber contained in the web. By carrying out like this, a heat | fever extensible composite fiber can fully be extended | stretched by the air through process of (c) mentioned later.

The thermal elongation start temperature of the thermally stretchable conjugate fiber is measured by the following method. A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used as a measuring device. A sample is prepared by collecting a plurality of fibers having a length of 10 mm or more so that the total mass per fiber length of 10 mm is 0.5 mg. After arranging the plurality of fibers in parallel, the fibers are mounted on the apparatus at a chuck distance of 10 mm. The melting point MP _C (° C.) of the resin constituting the core and the sheath are formed at a temperature rising rate of 5 ° C./min under the condition that the measurement start temperature is 25 ° C. and a constant load of 0.73 mN / dtex is applied. The temperature is raised to the higher melting point −10 ° C. of the melting point MP _S (° C.) of the resin. The atmosphere is nitrogen. At that time, the temperature at which the fiber showed an elongation of 1% is read, and that temperature is taken as the thermal elongation start temperature.

  When a plurality of embossed portions are formed on the web by the embossing device, the air-through step (c) is performed next. In the air-through process, hot air is blown to the web after embossing (hereinafter, the web in this state is referred to as “embossed web”) by an air-through method. The hot-extensible conjugate fiber contained in the embossed web is stretched by blowing hot air. For this purpose, it is preferable to set the temperature of the hot air blown to the embossed web to be equal to or higher than the heat extension start temperature of the heat-extensible composite fiber. In particular, the blowing temperature of the hot air is preferably equal to or higher than the melting point of the sheath component, which is a low melting point component, and lower than the melting point of the core component, which is a high melting point component. More preferably, it is not higher than the melting point of the high melting point component.

  The hot air blowing speed depends on the basis weight and thickness of the embossed web, but is preferably 0.2 m / sec or more, more preferably 0.3 m / sec or more, and 20 m / sec or less. It is preferable to set it to 15 m / sec or less. The hot air blowing speed is preferably 0.2 m / sec or more and 20 m / sec or less, and more preferably 0.3 m / sec or more and 15 m / sec or less. The blowing speed of the hot air is a value measured using MODEL 6162 and MODEL 0203 of ANEMOMASTER manufactured by Nippon Kanomax Co., Ltd. at a position 10 cm above the embossed web. The hot air blowing time is preferably 1 second or more, particularly preferably 5 seconds or more, and 40 seconds or less, provided that the temperature and speed of the hot air are within the above-mentioned ranges. It is preferable that it is 30 seconds or less especially.

  The heat-extensible composite fiber is stretched by blowing hot air. Since a part of the heat-extensible composite fiber is fixed by the embossed part formed in the previous step (b), it is the part between the embossed parts that extends. And since the heat extensible fiber is partially fixed by the embossed portion, the stretched portion of the stretched fiber loses its place in the plane direction of the embossed web and moves in the thickness direction of the embossed web. Thereby, the embossed portion is raised to form a convex portion, and the intended nonwoven fabric becomes bulky.

  As described above, a soft nonwoven fabric that is bulky and thick and has a good texture can be obtained. From the viewpoint of making these characteristics more prominent, in the production method of the present invention, before the embossing step (b) described above, the next step (d), that is, the heat-extensible composite fiber, It is advantageous to perform a step of temporarily shrinking the heat-extensible composite fiber by heat treatment at a temperature not lower than the glass transition point Tg of the resin constituting the resin and lower than the heat extension start temperature of the heat-extensible composite fiber. . The reason why the bulk of the nonwoven fabric is further increased by performing the step (d) will be described with reference to FIG. 1 described above.

The elongation of the heat-extensible composite fiber used in the present invention is performed on the embossed web obtained in the embossing step (b). Therefore, it is desirable that the heat-extensible composite fiber present in the embossed web is in a state where the degree of heat extension is the largest. By the way, as shown in FIG. 1, the heat | fever extensible composite fiber used by this invention has the property to shrink | contract at comparatively low temperature, and to expand | extend at higher temperature than it. Therefore, in order to maximize the degree of thermal elongation of the heat-extensible composite fiber, it is advantageous that the heat-extensible composite fiber present in the embossed web is in the state indicated by symbol A in FIG. is there. When the heat extensible conjugate fiber is in this state, in the figure, the fiber is extended to the extent represented by E _1. For this purpose, before the embossed web is formed, that is, before the embossing step (b), a relatively low-temperature heat is applied to the heat-extensible composite fiber to cause heat shrinkage. In the figure, the state indicated by symbol A is set. This corresponds to the above step (d). In order to obtain the state indicated by the symbol A, as described above, the thermally stretchable conjugate fiber is not less than the glass transition point Tg of the resin constituting the core and less than the thermal elongation start temperature of the thermally stretchable conjugate fiber. Heat treatment at a temperature is advantageous, and by applying this heat treatment to the cut raw cotton instead of the tow, non-uniform heat treatment due to fiber friction and non-homogeneous heat treatment due to overlapping of fibers can be prevented. The inventor has found that the state A is obtained, and the present invention has been completed based on this finding.

On the other hand, when the heat-extensible conjugate fiber in a state before being heat-shrinked is incorporated into the embossed web, the heat-extensible conjugate fiber in step (c) is E ₂ (<E ₁ ) in FIG. It expands only to the extent represented by. Moreover, in the step (c), the shrinkage of the fiber occurs before the heat-extensible conjugate fiber is stretched, which negatively affects the production of a bulky nonwoven fabric.

  In order to maximize the degree of thermal elongation of the heat-extensible composite fiber, the temperature of the heat treatment in step (d) is not less than the glass transition point Tg of the resin constituting the core, and the glass transition point Tg plus More preferably, the temperature is set to 40 ° C. or lower, and more preferably 60 ° C. or higher and 120 ° C. or lower.

  The glass transition point Tg described above is measured using a differential scanning calorimeter (DSC6200 manufactured by Seiko Instruments Inc.). A finely cut fiber sample (sample weight 2 mg) was subjected to thermal analysis at a heating rate of 10 ° C./min, and the intersection of the base line on the melting start side of the inflection point of each resin and the tangent line of the inflection point was Tg. And

  The heat treatment in the step (d) may be performed at any time as long as the embossed web is not formed. For example, it can be performed before (I) the web manufacturing process which is the process of (a). Alternatively, it can be performed after completion of the steps (II) and (b) and before the embossing step. It can be done at both time points (I) and (II). When (I) and (II) are compared, it is more preferable to carry out step (d) at the time of (I). The reason for this is that at the time of (I), the heat-extensible conjugate fibers are in a state of being separated from each other, and the degree of interference with each other is low. This is because when the web is manufactured by using the fiber as a raw material and the step (a) is produced, the web is in a plump state. On the other hand, when the step (d) is performed at the time of (II), when the heat-extensible composite fiber contracts, due to interference with other fibers, particularly friction with other wires, The fibers are easily arranged linearly in the web, and the bulk of the web is less likely to be higher than in the case (I).

  In the case of performing the step (d) at the time of (I), it is preferable to perform the heat treatment in a state where the heat-extensible composite fibers are dispersed in the air because a plump web is more easily formed. . In particular, the step (d) is performed inside a fiber spreader for opening the heat stretchable conjugate fiber, and while the fiber is spread, hot air is sent into the spreader to disperse the heat stretchable conjugate fiber. It is preferable from the point that a more plump web is obtained. The temperature of the hot air is set within the temperature range of the process (d) described above.

  Nonwoven fabrics produced in this way are used as constituent members of various absorbent articles such as sanitary napkins and disposable diapers, for example, surface sheets, using characteristics such as bulkiness, good texture, and softness. Preferably used. In addition to this application, for example, a second sheet (a sheet disposed between the top sheet and the absorber), a back sheet, a leak-proof sheet, a personal wipe sheet, a skin care sheet, and an objective wiper. It can also be suitably used. When using a nonwoven fabric for absorbent articles, such as a sanitary napkin, for example, it can distribute | arrange on an absorber so that the surface which has a convex part in this nonwoven fabric may face a wearer's skin. Moreover, the non-woven fabric manufactured by the manufacturing method of the present invention has a large inter-fiber distance due to an increase in thickness. Therefore, the liquid easily passes through the nonwoven fabric, and when the nonwoven fabric is used for the top sheet of the absorbent article, the liquid is quickly transferred to the absorbent body. As a result, the liquid spreading area on the non-woven fabric is reduced, and the wet feeling of the absorbent article wearer is reduced, and the absorbent article has an excellent wearing feeling.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, when the nonwoven fabric obtained by the production method of the present invention is wound with a winder and stored in a wound state, the bulk of the nonwoven fabric may be reduced by the tightening force. In such a case, when the nonwoven fabric is fed from the wound body, hot air may be blown onto the nonwoven fabric by an air-through method to recover the reduced bulkiness.

This invention discloses the manufacturing method of the following nonwoven fabrics further regarding embodiment mentioned above.
<1>
A web production process for producing a web containing a heat-fusible core-sheath composite fiber having a shrinkage rate at 80 ° C. of 0% or more and an elongation rate at 136 ° C. of 8% or more;
Embossing the web manufactured in the web manufacturing process and fixing the constituent fibers of the web at a plurality of embossed portions to obtain an embossed web, and air through to the embossed web A method of manufacturing a nonwoven fabric having an air-through process of blowing hot air in a method,
Prior to embossing, the heat-fusible core-sheath composite fiber is set to a temperature not lower than the glass transition point of the resin constituting the core, and the heat-fusible core-sheath composite fiber is set to a temperature lower than the thermal elongation start temperature. After heat treatment, the heat-fusible core-sheath composite fiber is once shrunk,
A method for producing a nonwoven fabric, wherein the hot air is blown in an air-through manner at a temperature equal to or higher than a thermal elongation start temperature of the heat-fusible core-sheath conjugate fiber, and the heat-fusible core-sheath conjugate fiber is elongated.
<2>
Before the web manufacturing step, the heat-fusible core-sheath conjugate fiber is not less than the glass transition point of the resin constituting the core and less than the thermal elongation start temperature of the heat-fusible core-sheath conjugate fiber. The manufacturing method according to <1>, wherein the heat-fusible core-sheath composite fiber is once shrunk by heat treatment at a temperature of 1.
<3>
In a state where the heat-fusible core-sheath composite fiber is dispersed in the air, the heat-fusible core-sheath composite fiber has a temperature not lower than the glass transition point of the resin constituting the core and the heat-fusible core-fiber conjugate fiber. The production method according to <2>, wherein the heat-fusible core-sheath conjugate fiber is temporarily contracted by heat treatment at a temperature lower than a thermal elongation start temperature of the dressable core-sheath conjugate fiber.
<4>
Prior to embossing, the heat-fusible core-sheath composite fiber is heat-treated at a temperature not lower than the glass transition point of the resin constituting the core and not higher than the glass transition point plus 30 ° C. The production method according to any one of <1> to <3>, wherein the core-sheath type composite fiber is once contracted.
<5>
The production method according to <4>, wherein polyethylene terephthalate or polypropylene is used as the fiber-forming resin component.
<6>
The production method according to <4> or <5>, in which a crystalline thermoplastic resin having a melting point lower by 20 ° C. or more than the fiber-forming resin component is used as the thermal adhesive resin component.
<7>
The manufacturing method according to any one of <4> to <6>, wherein the crystalline thermoplastic resin is made of a polyolefin resin or a crystalline copolyester.
<8>
The heat-fusible core-sheath type composite fiber has a breaking elongation (JIS L-1015: 2005 8.7.1 method) of 130% or more, particularly 170% or more, preferably 1200% or less, particularly 900. % <1> thru | or <7> manufacturing method any one of which is preferable.
<9>
<1> to <8>, wherein the heat-fusible core-sheath conjugate fiber has a 120 ° C. dry heat shrinkage ratio (JIS L-1015: 2005 8.15 b) of less than −1%. Manufacturing method.
<10>
The heat-fusible core-sheath conjugate fiber comprises a first resin component and a second resin component having a melting point or softening point lower than the melting point of the first resin component, and the second resin component is at least on the fiber surface. A part of it is continuously present in the length direction,
The heat-fusible core-sheath composite fiber has a thermal elongation rate of 0.5% or more at a temperature 10 ° C. higher than the melting point of the second resin component, and in the case of a resin having no melting point, 10 ° C. higher than the softening point. The production method according to any one of <1> to <9>, wherein the production method is 20% or less.
<11>
<12> The manufacturing method <12> according to any one of <1> to <10>, wherein the web is composed of only the heat-fusible core-sheath composite fiber.
The web includes the heat-fusible core-sheath composite fiber and other fibers,
The ratio of the said other fiber is a manufacturing method any one of said <1> thru | or <11> which are 10 mass% or more and 90 mass% or less with respect to the mass of the said web.
<13>
The heat-fusible core-sheath composite fiber includes a low melting point component and a high melting point component,
The hot air blowing temperature is preferably not less than the melting point of the low melting point component and less than the melting point of the high melting point component, not less than the melting point of the low melting point component to not more than the melting point of the low melting point component + The production method according to any one of <1> to <12>, further preferably less than the melting point.
<14>
The hot air blowing speed is preferably 0.2 m / sec or more, more preferably 0.3 m / sec or more, preferably 20 m / sec or less, and preferably 15 m / sec or less. The production method according to any one of <1> to <13>, which is more preferable.
<15>
The hot air blowing time is preferably 1 second or more, more preferably 5 seconds or more, preferably 40 seconds or less, and more preferably 30 seconds or less <1> to <14> The manufacturing method of any one of 14>.
<16>
The temperature of the heat treatment is preferably set to a temperature not lower than the glass transition point of the resin constituting the core of the heat-fusible core-sheath conjugate fiber and not higher than the glass transition point plus 40 ° C. The production method according to any one of <1> to <15>, wherein it is further preferable to set the temperature to be equal to or lower than C.
<17>
The nonwoven fabric manufactured by the manufacturing method of any one of said <1> thru | or <16>.
<18>
The nonwoven fabric according to <17>, which is used as a surface sheet of an absorbent article.
<19>
The absorbent article provided with the nonwoven fabric manufactured by the manufacturing method of any one of said <1> thru | or <16>.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
(1) Manufacture of heat-extensible conjugate fiber A heat-extensible conjugate fiber was produced by the following method based on the description in Example 1 of JP-A-2007-303035. However, in this example, the drying performed before the cutting of the fibers was performed at room temperature in order to prevent the fibers from expanding and contracting. Polyethylene terephthalate (PET) is used for the core component (fiber-forming resin component), and high-density polyethylene (HDPE) is used for the sheath component (thermoadhesive resin component), and melted to a mass ratio of core: sheath = 50: 50. Resin was discharged and spun to form a composite fiber. The undrawn yarn obtained by this operation was cold drawn, and then the yarn was immersed in an aqueous solution of a hydrophilic fiber treating agent to give mechanical crimps. Next, the fiber length was cut to 46 mm. The obtained heat-extensible composite fiber had a single yarn fineness of 4.2 dtex, a heat shrinkage rate at 80 ° C. of 2.6%, and a heat extension rate at 136 ° C. of 8.0%.

(2) Manufacture of nonwoven fabric The heat-extensible conjugate fiber obtained in (1) was opened in the air in a spreader. At this time, the temperature of the hot air sent to the spreader was 90 ° C. As a result, the heat-extensible composite fiber was thermally contracted.
The web after heat shrinkage was supplied to a card machine to produce a web having a basis weight of 40 g / m ² . The web was embossed to form an oblique grid-like embossed portion with a line width of 0.5 mm. The formation area ratio of the embossed part in a plan view of the web was 14%. The embossing temperature was 124 ° C.
Hot air was blown on the embossed web thus obtained by an air-through method. The hot air temperature was 136 ° C., the hot air speed was 0.5 m / min, and the web conveyance speed was 10 m / min. The heat-extensible conjugate fiber was thermally stretched by blowing hot air to obtain the desired nonwoven fabric.

[Example 2]
In Example 1, the heat-shrinkable composite fiber in the web was formed by blowing hot air at 85 ° C. to the web by air-through method after the web was formed and before embossing after the web was not formed. Was heat shrunk. Except for this, a nonwoven fabric was obtained in the same manner as in Example 1.

[Comparative Example 1]
Based on the description in Example 1 of JP-A-2007-303035, a PET / PE core-sheath composite fiber was produced. This fiber had a thermal shrinkage rate of -1% at 80 ° C (ie, a thermal elongation rate of 1%) and a thermal elongation rate of 136% at 136 ° C. Moreover, in Example 1, the heat processing before web formation was not performed. Except for this, a nonwoven fabric was obtained in the same manner as in Example 1.

[Comparative Example 2]
In Example 1, heat shrinkage before web formation was not performed. Except for this, a nonwoven fabric was obtained in the same manner as in Example 1.

[Comparative Example 3]
In Example 1, heat shrinkage before web formation was not performed. In Example 1, the order of embossing and air-through hot air blowing was switched. Except for this, a nonwoven fabric was obtained in the same manner as in Example 1.

[Evaluation]
About the nonwoven fabric obtained by the Example and the comparative example, the thickness under 50 g / cm < ² > load was measured with the automated compression tester (model KES FB3-AUTO-A) of Kato Tech. Moreover, the obtained nonwoven fabric was used as a surface material of a sanitary napkin, and the degree of liquid spreading was measured by the following method. These results are shown in Table 1 below.

[Measurement method of degree of liquid spreading]
The measurement was performed using a sanitary napkin (manufactured by Kao Corporation: Laurie Skin Clean Guard, Normal Daily Wings Without Wings October 2014) as an example of an absorbent article. The surface sheet is removed from the sanitary napkin, and instead of the nonwoven fabric to be measured, the surface sheet on the napkin absorbent body (on the skin contact surface of the napkin absorbent body) has an uneven surface. The surface on the opposite side of the napkin was fixed so as to face the absorbent body of the napkin. Thereby, a sanitary napkin for evaluation using a nonwoven fabric to be measured as a surface sheet was obtained. When removing the top sheet from the napkin, the front and rear end portions of the napkin were cut in the width direction, and then the top sheet was peeled off from the napkin while adjusting the force so that the absorber was not broken.
Next, 3 g of defibrinated horse blood was injected into the obtained sanitary napkin, and then attached to a movable female lumbar model. After wearing shorts on it, the walking speed was 100 steps / minute (50 m / minute). And walked for 10 minutes. Thereafter, 3 g of defibrinated horse blood was further injected and allowed to walk for 10 minutes at the same speed. Thereafter, the napkin was removed from the model, the surface sheet was further removed from the napkin, the area where the horse blood spread on the surface sheet was measured, and the value was taken as the liquid spread value. The area was measured by the following method. A transparent film was layered on the top sheet, and the area where horse blood spread was painted black. The black part was cut out from the film and the mass was measured. And the area where horse blood spread was calculated | required from the following formula | equation.
Horse blood spread area = mass of painted film ÷ mass of the whole transparent film × area of the whole transparent film As the defibrinated horse blood, equine defibrinated blood manufactured by Japan Biotest Laboratories Co., Ltd. was used. The viscosity of this horse defibrinated blood was less than 15 mPa · S as measured with a (B type) viscometer TVB-10M manufactured by Toki Sangyo Co., Ltd. (measurement temperature 25 ° C., rotor L adapter).

  As is clear from the results shown in Table 1, it can be seen that the nonwoven fabric obtained in each example is thicker and bulkier than the nonwoven fabric of the comparative example having the same basis weight. Moreover, it turns out that the sanitary napkin using the nonwoven fabric obtained by each Example is a thing with a small extent of a liquid expansion compared with the sanitary napkin using the nonwoven fabric of a comparative example.

Claims (4)

A web production process for producing a web containing a heat-fusible core-sheath composite fiber having a shrinkage rate at 80 ° C. of 0% or more and an elongation rate at 136 ° C. of 8% or more;
Embossing the web manufactured in the web manufacturing process, and embossing process to obtain an embossed web by fixing the constituent fibers of the web at a plurality of embossed portions formed thereby, and air through the embossed web A method of manufacturing a nonwoven fabric having an air-through process of blowing hot air in a method,
Using short fibers as the heat-fusible core-sheath composite fiber,
Prior to embossing, the heat-fusible core-sheath composite fiber is heat-treated at a temperature not less than the glass transition point of the resin constituting the core and lower than the thermal elongation start temperature, and the heat-fusible core-sheath Once the mold composite fiber is shrunk,
A method for producing a nonwoven fabric, wherein the hot air is blown in an air-through manner at a temperature equal to or higher than a thermal elongation start temperature of the heat-fusible core-sheath conjugate fiber, and the heat-fusible core-sheath conjugate fiber is elongated.   Prior to the web manufacturing step, the heat-fusible core-sheath type composite fiber is not less than the glass transition point of the resin constituting the core and less than the thermal elongation start temperature of the heat-fusible core-sheath type composite fiber. The manufacturing method according to claim 1, wherein the heat-fusible core-sheath conjugate fiber is once shrunk by heat treatment at a temperature of 5 ° C.   In a state where the heat-fusible core-sheath type composite fiber is dispersed in the air, the heat-fusible core-sheath type composite fiber is brought to a temperature above the glass transition point of the resin constituting the core, and The production method according to claim 2, wherein the heat-fusible core-sheath composite fiber is temporarily shrunk by heat treatment at a temperature lower than the thermal elongation start temperature of the dressable core-sheath composite fiber.   Prior to embossing, the heat-fusible core-sheath composite fiber is heat-treated at a temperature not lower than the glass transition point of the resin constituting the core and not higher than the glass transition point plus 30 ° C. The manufacturing method according to any one of claims 1 to 3, wherein the core-sheath composite fiber is once shrunk.

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